Bump detector



June 1962 c. P. GRANT ETAL 3,037,381

BUMP DETECTOR Filed May 15, 1959 3 Sheets-Sheet 1 INVENTORS. GILBERTFORRESTER CLYDE P. GRANT ROBERT L. SMITH ATTORN EYS June 5, 1962 c. P.GRANT ETAL 3,037,381

BUMP DETECTOR Filed May 13, 1959 3 Sheets-Sheet 2 Eli 74 a? l I I a II\l 62 Fl G. 4 INVENTORS.

GILBERT FORRESTER CLYDE R GRANT ROBERT L. SMITH ATTORN EYS June 5, 1962c. P. GRANT ET AL BUMP DETECTOR 3 Sheets-Sheet 3 Filed May 13, 1959AAAAAAAA ER E VOR

NFG N l. L w w W T T R T B M A UGO GCR United States Patent 3,037,381BUMP DETECTOR Clyde 1. Grant, Gorham, Gilbert Forrester, Falmouth, andRobert L. Smith, Gorham, Maine, assiguors to S. D. Warren Company,Boston, Mass., a corporation of Massachusetts Filed May 13, 1959, Ser.No. 812,895 6 Claims. (Cl. 73-159) This invention relates to improvedmeans for detecting abrupt changes in caliper of a moving web offlexible material such as paper.

In the manufacture of fine paper, it has been found 162181131? toinspect a paper web for defects just before it is cut mto sheets and toprovide means for automatically sorting and separting sheets that havedefects from sheets that are free of defects. Various types of devicesare used for inspecting the web for predetermined types of defects andfor generating an electrical signal which will operate the sortingmechanism at the proper time to eliminate a defective sheet.

Detecting bumps or abrupt changes in caliper of a web has beenespecially bothersome. While devices have been made which will detectsubstantially all bumps or abrupt changes in caliper of a certainmagnitude, they have been subject to certain limitations, as, forexample, accuracy only at low web speeds or false indications of a bumpdue to certain physical or chemical characteristics of the web, as, forexample, moisture. V

The object of this invention is to provide a new type of bump detectorwhich is free of the limitations attendant to bump detectors heretoforedevised.

A more specific object of this invention is to provide means fordetecting sharp changes in the caliper of a moving web and forgenerating an electrical signal each time an abrupt change isdiscovered.

Another specific object of this invention is to provide a bump detectorcapable of operating efliciently regardless of the physical and chemicalcharacteristics of the web being inspected.

Other objects and many of the attendant advantages of the presentinvention will be more readily appreciated as the invention becomesbetter understood by reference to the following detailed descriptionwhen considered in connection with the accompanying drawings, wherein:

FIG. 1 is a perspective view showing a plurality of bump detector skidspositioned in operating relation to a paper web;

b FIG. 2 is an enlarged plan view of one of the skid memers;

FIG. 3 is a sectional view in elevation of the assem bly of FIG. 1;

FIG. 4 is a sectional view taken along line 44 of FIG. 3;

FIGS. 5 and 6 are enlarged fragmentary side views of two modified formsof skid; and

FIG. 7 is a schematic diagram of an electric system employed with theskids to generate an electrical signal when a bump is detected.

Referring now to FIG. 1, there is shown a portion of a bump detectorassembly for use in a machine for (1) inspecting a paper web forpredetermined types of defects, (2) cutting said web into sheets, and(3) separating defective sheets from sheets that are free of defects.Such a machine is disclosed in our copending application for Apparatusfor Inspecting, Cutting, and Sorting Paper, Serial No. 776,342, filedNovember 25, 1958.

The bump detector assembly comprises a horizontal beam 2 mounted aboveand slightly upstream of a roll 4 which supports a moving paper web 6.Roll 4 may be a driven roll, or, if the paper is driven by other rolls,it may be simply an idler roll. Attached to the beam 2 by means of bolts8 is a series of brackets 10 each having a pair of parallel-spacedhorizontal arms 12 which project in a downstream direction away frombeam 2. Brackets 10 extend in an even line along beam 2 and function tosupport a plurality of skids identified generally by numeral 14.

Referring now to FIGS. 1, 2, and 3, each skid 14 comprises a bodyportion made up of two relatively thick plates 16 and 18 held insuperposed relation by screws 20 and a rectangular metallic plate 22. Asubstantial portion of plate 22 is sandwiched tightly between plates 16and 18. The latter are provided with matching semicylindrical grooveswhich define a channel in which is held a tube 24 whose ends containbearings 26 and 28. Rotatably journaled in these bearings and extendingbeyond the ends of tube 24 is a shaft 30. The ends of shaft 30 aresupported by the two arms 12 of bracket 10. Arms 12 are provided withV-shaped notches 32 which function as seats for the ends of shaft 30.The latter are releasably held down in notches 32 by latches 3'4 whichare pivotally secured to arms 12' by means of screw bolts 36 which arescrewed into tapped openings 38 in arms 12. Bolts 36 are made tight soas to prevent latches 34 from turning as a result of any vibration ofthe apparatus during operation. Tube 24 is located so that the center ofgravity of the skid is slightly forward of shaft 30'.

Although each plate 22 may be prefectly flat at its forward edge, it ispreferred that each one be bent to form a lip 40 at that edge. Lip 40makes the edge more rigid and reduces any tendency for the plate to flexcornerwise or about the line of symmetry of the skid. The line ofsymmetry of the skid is indicated by the broken line C-C in FIG. 2.Accordingly, any force applied to a portion of plate 22 will cause it tobend or flex along a line running parallel to its forward edge. Sinceplate 22 is anchored only along one edge, it is similar to a cantileverbeam; and, accordingly, any flexing which it experiences tends to occuralong the line of the forward edges 42' of plates 16 and 18.

Assuming now that web 6 has a bump in its top surface and that it istraveling at an appreciable speed, as, for example, 200 feet per minute,the bump will produce a sharp blow on one of the skids as it travelsover roll 4. Because the center of gravity of the skid is downstream ofshaft 30, the skid will have a moment of inertia that tends to preventthe skid from pivoting upward. Consequently, the metal plate 22 willyield first to absorb the elfect of the blow and to allow the bump topass on downstream, and almost instantaneously thereafter, the skid willpivot upward in reaction to the energy absorbed by the plate. Inyielding to the bump, the metal plate bends upward (i.e., flexing)relative to the body portion of the skid. This flexing action issufiiciently small in magnitude and occurs so fast as not to bediscernible to the naked eye. However, it is of suflicient magnitude tobe detected.

In the illustrated embodiment of the invention, the deflection of themetal plates in response to bumps or rapid changes in web caliper isdetected by means of a crystaltype phonograph pickup head identifiedgenerally by numetal 46. The head is provided with a pair of flanges 48and 50 which are provided with holes to receive screws 52 whichcooperate with nuts 54 to anchor the head to a bracket 5'6. Preferably,but not necessarily, flanges 48 and 50 are sandwiched between resilientwashers 58 made of rubber or other suitable material. Bracket 56 is madeof rigid metal and has upturned sides 60 and 62 which prevent it fromflexing about its center. The bracket is fastened by short screws 64 and66 to the top half 16 of the body portion of the skid and is oriented sothat the forward end of the pickup head overlies metal plate 22. Pickup46 is disposed slightly to one side of the center line C-C of the skid.Secured to the cartridge in the hole normally occupied by a phonographneedle is a wire rod element 68 comprising a first inclined portion 70formed integral with a second horizontally extending portion 72. The topend of portion 70 is secured within the pickup head by a set screw 74.To the free end of portion 72 is secured a conventional hex nut 76.Mounted in nut 76 is a screw 78, Screw 78 is turned down into snug, butnot tight, contact with plate 22. at a point approximately half-waybetween its side edges and preferably, but not necessarily, it contactsthe plate at a point offset from the line of contact of the plate withroll 4, as in FIG. 3. This assures optimum and substantially uniformresponse for all deflections caused by bumps anywhere along the entirewidth of the skid.

The pickup head has two output terminals 80 and 82 which are connectedby means of a two-wire cable 86 to the output circuit illustrated inFIG. 7.

Referring now to FIG. 7, the two terminals of pickup head 46 areconnected to a band pass filter. More particularly, they are connectedin series with two capacitors 92 and 94, two resistors 96 and 98, athird capacitor 100, and a third resistor 182 which is part of apotentiometer 104. Terminal 82 is grounded. A resistor 106 is connectedat one end to the juncture of capacitors 92 and 94 and at the other endto ground. Another resistor 108 is connected between capacitor 94 andresistor 96 and at the other end to ground. A capacitor 110 is connectedon one side to the juncture of resistors 96 and 98 and at the other sideto ground. Still another capacitor 112 is connected on one side toground and on the other side to the juncture of resistor 98 andcapacitor 100. Capacitors 92 and 94 and resistors 106 and 108 havevalues suitable to pass all signals above approximately 200 cycles. Theremaining resistors and capacitors have values suitable to pass allsignals below 2000 cycles. As a result, spurious 60-cycle and otherlowfrequency signals resulting from machine vibration or motor hum andany stray high frequency signals are eliminated, and only signalsbetween 200 and 2000' cycles are passed. It has been found that signalsgenerated by bumps in a paper web are concentrated in that band and thatelimination of all other signals provides a great increase in response.

Potentiometer 104 has a slider 116 which is coupled directly to thecontrol grid 118 of the left-hand half of a twin triode 120. Bothcathodes 122 are connected to ground. The rightand left-hand plates 124and 126 are connected in parallel with a positive voltage supply 128through load resistors 130 and 132 respectively. Plate 124 is connectedto the right-hand grid 134 by a capacitor 136. A resistor 138 isconnected on one side to ground and on the other side to the juncture ofgrid 134 and capacitor 136. Capacitor 136 and resistor 138 function as adifferentiating circuit. Plate 126 is connected by a capacitor 140 tothe control grid 142 of the pentode sec tion of a combinationpentode-triode tube 144. A resistor 146 is connected between ground andthe junctures of capacitor 140 and control grid 142. Capacitor 140 andresistor 146 function as a differentiating circuit. The plate 148 of thepentode is connected by a load resistor 150 to voltage supply 128. Thescreen gn'd 152 is connected by load resistor 154 to the same voltagesupply. The suppressor grid'156 and pentode cathode 158 are connected toground through a resistor 160. Suppressor grid 156 is connected also tovoltage supply 128 through a resistor 162.

The control grid 164 of the triode section of tube 144 is connected by acapacitor 166to plate 148 of the pentode. A capacitor 168 is connectedbetween ground and the juncture of grid 164 and capacitor 166. Aresistor 170 is connected in parallel with capacitor 168.

The triode plate 172 is connected to a second positive voltage supply174 through the coil 176 of a switching it relay 178. The latter has twonormally closed switch contacts 180 and 182 which are opened when coil176 is energized. Contact 180 i s connected to an oscillator 184, andterminal 182 is connected to a magnetic recorder 186.

Operation of the system of FIG. 7 will now be described. When a bump inthe moving paper web strikes a skid, it causes flexing of its metalplate 22. This in turn causes movement of screw 78 which in turn causesdistortion of the crystal in the pickup head. This distortion istranslated into an electrical signal having a generally sine wave shape.This signal is filtered and applied to grid 118 for amplification by theleft-hand section of tube 120. Slider 116 is adjusted for proper gain.The amplifier signal is fed to grid 134 for further reamplification inthe right-hand section of tube 120. The amplified signal appearing atplate 126 is differentiated by capacitor 140 and resistor 146, and theresulting pulses are applied to control grid 142 of the pentode sectionof tube 144. This pentode section is always conducting but below thelinear portion of its operating wave. Hence, it amplifies positivepulses to a greater extent than negative pulses. These positive andnegative pulses are amplified and inverted and applied to the controlgrid 164. The right-hand half of tube 144 is normally conducting but isdriven to cutoff by the negative pulses applied to grid 164. When theright-hand half of tube 144 is driven to cutoff, coil 176 isdeenergized, and contacts 180 and 182 reclose to couple oscillator 184to recorder 186. The right-hand section of tube 144 remains cut off fora short while after the negative pulse applied to its grid 164 haspassed. This is necessary in order to allow the coil 176 to bedeenergized long enough for contacts 180 and 182 to close. Theright-hand half of tube 144 is kept off by the voltage appearing acrosscapacitor 168.

The time duration of the cutoff period of the tube is determined by thecharge across capacitor 168 and the RC time constant of capacitor 168and resistor 170. The negative voltage across capacitor 168 bleeds offthrough resistor 170, and the right-hand half of the tube begins toconduct again when the voltage across capacitor 168 returns above thecutoff voltage.

It has been found that the signal generated by a bump is of relativelyshort duration and decays rapidly to zero. Thus, the generated signaltrain is so short as to appear as a single negative pulse at grid 164.It is believed to be obvious that any positive pulses which appear atgrid 164 are so small as not to interfere with operation of the circuitas just described.

It is to be noted that while the system shown in FIG. 7 includes arecorder for preserving the short ouput of oscillator 184, such arecorder is not necessary and is illustrated simply to show how thepresent invention may be substituted for the bump detector system of theapparatus disclosed in our copcnding application Serial No. 776,342. Theoutput of the oscillator passed by relay 178 need not be applied to arecorder but may, for example, be applied to an alarm system. Similarly,the oscillator may be omitted and relay 178 may be employed to op eratesome other device, as, for example, a warning light.

It is to be understood that the pickup heads for several skids may beconnected in parallel to a single electrical system like the one shownin FIG. 7, or each pickup head may have its own system. It is furthercontemplated that the phonograph pickup heads need not be of the crystaltype but may be of the magnetic type as well.

The invention is not limited to the exact skid shown in FIGS. 1 and 2.In fact, it is preferred to attach to the underside of metal plate 22 aseparate riding shoe 1% (FIG. 5) which can be readily replaced whenworn. Shoe is attached by means of a plurality of screws 192.Alternatively, the shoe may be attached by a suitable adhesive or may beshaped or molded so that it may be attached without screws, as bygripping the plate edge in a tight groove. Preferably, the edges of theshoe are beveled as shown at 194 so as to provide better contact withthe paper Web. The shoe may be made out of any suitable material,preferably a plastic. Teflon has been found to be especially suitable.

It is to be understood also that the metal plate 22 need not have thesharp right-angle lip 40. Instead, it the metal plate is suificientlyrigid, the lip may be omitted entirely. Alternatively, the lip may beformed by a more gentle curve, like the lip 40a shown in FIG. 6.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It is to beunderstood, therefore, that the invention is not limited in itsapplication to the details of construction and arrangement of partsspecifically described or illustrated, and that Within the scope of theappended claims, it may be practiced otherwise than as specificallydescribed or illustrated.

We claim:

1. Apparatus for detecting abrupt changes in caliper of a moving web ofpaper comprising a roll for supporting said web, a skid support disposedadjacent to said roll, a skid having a body portion pivotally secured tosaid support with a flexible extension urged into light contact withsaid moving web, a transducer mounted on said body portion, and a probeon said transducer coupled to said flexible extension and responsive torelative motion between said extension and said body portion fortranslating flexing of said skid caused by an abrupt change in caliperof said web into an electrical signal indicative of said abrupt changein caliper.

2. Apparatus for detecting sharp changes in caliper of a moving web ofpaper comprising a horizontal roll for supporting said moving web, askid supporting member located above and extending parallel to saidroll, a skid comprising a relatively thick fiat substantially inflexiblebody member pivotally secured to said skid supporting member and arelatively thin flexible but torsion-resistant member for engaging saidmoving web along a transverse line, an elongated pickup probe in contactwith said torsion-resistant member and movable in response to flexing ofsaid same member relative to said body member, a transducer elementmounted on said body member and supporting said pickup probe forproducing an electrical signal in response to movement of said probe,and means for amplifying said signal.

3. Apparatus as defined by claim 2 wherein said transducer is acrystal-type phonograph pickup cartridge.

4. Apparatus as defined by claim 2 wherein said transducer is amagnetic-type phonograph pickup cartridge.

5. Apparatus as defined by claim 2 further including means connectingsaid transducer and said amplifying means for eliminating signals having(1) a frequency below 200 cycles and (2) signals having a frequencyabove 2000 cycles.

6. Apparatus for detecting sharp changes in caliper of a moving web asit moves over a roll, comprising a fixed member located above andextending transversely of the moving web, a skid pivotally attached tosaid fixed member, said skid comprising first and second fiat relativelythick rigid members and a third fiat flexible relatively thin memberhaving a first portion thereof sandwiched tightly between said first andsecond members, said third member having a second portion in engagementwith said moving web, a phonograph pickup head attached to one of saidfirst and second members, said pickup head having a pickup element inengagement with the said second portion of said third member, and signalgenerating means connected to said pickup head for producing an outputsignal each time said pickup element is moved by flexing of said thirdmember.

References Cited in the file of this patent UNITED STATES PATENTS2,221,516 Hathaway Nov. 12, 1940 2,392,010 Stevens Jan. 1, 19462,405,133 Brown Aug. 6, 1946 2,620,655 Priest Dec. 9, 1952 2,764,018Enabnit Sept. 25, 1956 2,942,248 Huggins June 21, 1960

